DSL over Fiber

DSL over Fiber
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ronpin @ 13th May 10:08AM:
DSL over Fiber

I keep hearing that DSL over fiber doesn't work -- but how can that be true?

If I hookup a DSL modem WAN port (telco side) to a copper-to-fiber media converter -- the converter should faithfully recreate whatever signal is present on the copper -- even the 256 discrete multi-tones *analog* signal of VDSL. The receiving converter should faithfully recreate the 256 DMT signal at the other end. Am I missing something?

As long as the DSL signal "gets-to stay analog" -- what's the problem?
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tschmidt @ 13th May 10:29AM:
Re: DSL over Fiber

Issue is not technical feasibility but does it make sense to do so? In one word - cost.

If you have fiber why would you limit it to a single DSL connection vs taking advantage of its capability to transport lots of customers. Transporting analog DSL over fiber does not make economic sense.

Cablecos and Verizon FIOS do something similar to what you propose. They use analog techniques to carry RF TV over fiber. At NODE they convert optical signal to electrical for deliver over the short customer coax.

/tom

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ronpin @ 13th May 10:36AM:
Re: DSL over Fiber

Yes -- silly to place a DSL on fiber -- *BUT* -- that's what you'd be *forced* to do if you wanted to "retrofit" a fiber from your house -- to a FTTN node. Telco's want every customer served by the same interface -- no exceptions for those pesky FTTH resellers (who'd really prefer a straight OC12 backbone feed from the telco, no DSL)

So, I definitely see the sillyness -- but also the opportunity for FTTH -- in spite of DSL.
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dslwanter @ 13th May 01:06PM:
Re: DSL over Fiber

DSL isn't feasible over fiber, period. DSL is a radio signal that dies after 3 miles. If it was easy to repeat, telco's would be able to offer 6mbps DSL to their entire blueprint. The signal would be more reliable over fiber since fiber is virtually transparent to EMI unlike copper.

Verizon has the right idea, so do cable companies offering DOCSIS via FTTH in new areas. AT&T is on the wrong track and will still have to deal with "distance" issues. Why? Because they won't ditch xDSL technology.

If a company is going to spend the money to build a fiber network, they're going to look to save on ways to provide service and DSL wouldn't be a smart choice.
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ronpin @ 13th May 01:48PM:
Re: DSL over Fiber

said by dslwanter :

DSL isn't feasible over fiber, period. DSL is a radio signal

Your cell phone antenna output would happily modulate a media converter (connected via coax). It is analog modulation with digital encoding -- and for VDSL it contains 256 "discreet multi-tones" (oh they're very discreet :) ) I still see no technical reason -- but yes, apparently no telco will spend ~$200 per customer to extend a DS-1 line via media converters.
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